my response to an authoritiarian demand on the street is proportionally calm, firm, and polite. mostly i try to shoot with confidence, giving the appearance that i'm supposed to be there doing what i'm doing. i'll get the occasional challenge, no biggie. based on my experience, i seem to have more difficulty with folks with arabic background. i think i understand the sensitivity to photo-taking on their part.
one incident in Detroit's Eastern Market this summer was memorable. i had just snagged a couple of exposures of an arabic woman wearing the burkah in what seemed lovely light. kept walking after the shots. about a block away i become aware that i'm being chased. this fellow grabs my shoulder from behind, stops me, and starts proclaiming loudly right in my face that i've insulted him, his wife, and family. he's angry. he wants my film. now i'm kinda large (6'3" and about 230#) but no matter, this guy's aggressive. i looked him in the eye and said slowly, "you know, i took those pictures because your wife is beautiful and that's what i try to shoot: beauty. i'm sorry you see it differently. i meant no disrespect." he stared hard at me. i thought for a moment he was looking to have a go. then he said, "oh, okay, i didn't know." and he walked away without another word. sometimes a compliment can defuse a confrontation.